Many processors support interfaces intended for debugging, profiling, or aiding the manufacturing process of a chip as it is tested during pre-packaging and after packaging. These support interfaces allow access to internal states of the chip. For example, this includes support for post-shipment chip return failure analysis. Such access is open and frequently implemented via a low pin count interface to the CPU, such as a scan chain interface. However, when a processor contains processor specific secrets, or is requested to perform sensitive (secure and trusted) operations, these support interfaces put these secrets at risk of discovery. That is, preservation of sensitive information can be compromised due to unfettered access to the processors and memory of each of the conventional digital computer systems through these support interfaces. Thus, it would be advantageous to provide a solution that can provide a secure scan chain interface.